Laminated punching with small air-gap between teeth



Dan, 17, 19350 A. B. REYNDERS- LAMINATED. PUNCHING WITH SMALL AIR GAP BETWEEN TEETH Filed Oct. 14, 1935 INVENTOR Ari/7MB fieynders.

WITNESSES:

ATTORNEY fiZh 4 d Patented Dec. 17, 1935 UNITED STATES PATENT OFFIQE LAlWINATED PUNCHING WETH SMALL AIR-GAP BETWEEN TEETH Arthur B. Reynders, Springfield, Mass, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 14, 1933, Serial No. 693,562

4 Claims. (01. 1'7236) This invention relates to a method for obtaining a small air-gap between the teeth in a laminated punching, and to the resultant magnetizable core structure which is made up from a punching, by punching the winding-receiving perforations so as to leave a complete magnetizable bridge over the same, between the perforations and the periphery of the punchings. I then a stack of such punchings. slit the bridge-material between this perfora- 5 It is common practice, particularly in the rotor tion and the periphery of the punching. This slitmembers oi electrical motors, with special referting operation is m y a Shearing operation r ence to induction motors, to utilize open slots for sulting in a cutting of the punching-material, the Winding-conductors in the magnetizable ro- W h m v y app portion of the tor core. That is, the punchings or laminations punching-material as is the Case With the ordi- 10 of which the core is composed are provided with y Dllhohhhddie method 111 Whioh a d e s perforations which are disposed near the windingforced through the material. The punching o Carry ng periphery. The punching material b the perforation and the slitting can be done in tween these perforations is called teeth; and these a singl machine-operationteeth are separated from each other, in such The p between teeth can be Varied to a 15 open-slot designs, by causing narrow t siderable extent by skewing the teeth or bending sion of the perforation to extend from the windthem out of the planes of the pilhohings, So that ing-carrying portion of the perforation to the said the effective lengths of the toothed tips, in a periphery of the punching. The advantages of ollmfelehtial direction, are reduced.

this common open-slot construction is mainly the In t e a p y drawing, Figure 1 is a 20 reduced slot-leakage and hence th higher torque full-scale transverse cross-sectional View of a dywhich is obtainable, at a somewhat better power name-electric machine having my invention pfactor. There is also a reduction in that portion plied to its rotor p hi ss, 2 s a nla ed of the motor losses which are due to tooth-pulsafragmentary edgewiew of a p ura ty o the rotor tion fluxes, and usually there is a slight increase Duhohihgs embodying y invention, and ig- 3 25 in the noise of operation, due to the open-slot is an enlarged m n ary endiew thereof. construction as contrasted from the closed-slot The dy c machine Co sists of a cgnstrucfion 11 th is 11 known stator I and a rotor 2 separated by the main air- There are certain practical physical limitations gap 3 of the ac ine. The el ctrically operato the dimensions obtainable in such designs, with tiVe peripheries of t Sta o a d rotor, that is, 30 the ordinary punch-and-die method of making the ihhel' P p y of t St a d the oute punchings. The limitation which my invention periphery of the rotor, we p v d d W t Windovercomes is the narrowest slot which can be ing-reoeivihg perforations 5 and 5, respectively, punched across the bridge which lies between the in which are disposed e Stator a d rotor Windwinding-receiving perforation and the periphery ihgwonduotors 7 a p ve y 35 of the punching. n" a die is utilized to make this n th win I h v ll d my nv slot, the narrowest slot that can be made is limtion as being pp to the laminated et ited by the requirement that there must be a reaable rotor core 2. This core is built up from a sonable life of the die or tool, which limits the stack of punchings ii having alined Winding-re- 40 slot to about at of an inch in width, or at the eeiving p f ations 6 spaced somewhat from the 40 best, about 25 mils. This means that the tips of winding-C y p p y of the p ch gs So the teeth have an air-gap of at least 25 mils. or as to prov de maghetizoble bridges l2 over the of an inch between them, with the ordinary winding-carrying perforations 6, that is, between punch-and-die method of making punchings. said perforations and said periphery. The teeth 5 In small-motor design, it is frequently found between the perforations are designated by the that this is a much larger air-gap between teeth numeral l3, and it will be noted that the tips than is desired, so that the electrical design has of these teeth have peripheral portions l4 overheretofore been a compromise necessitated by hanging the perforations 6. this limitation in the narrowest practical slot In accordance with my invention, the bridges which could be obtained between the teeth. l2, which are disposed between the teeth at said 50 In accordance with my invention, I do not winding-carrying periphery of the rotor, are punch the air-gap between the teeth by forcing a slit from said perforations 5 to said periphery, die through the material of the punching so as to so that the tips of the teeth iii are physically sepremove a portion of the punching-material. On arated from each other, but are substantially the contrary, I make an ordinary closed-slot touching each other. This produces the elfect 55 of an extremely narrow air-gap I between the teeth, and the width of this tooth air-gap can be considerably varied, and in general practice is increased somewhat, by skewing the teeth of the punchings, or bending the teeth out of the planes of the punchings, as shown in Fig. 2, so that the tooth air-gap l 5 can have its optimum width, as desired by the electrical designer, without being limited to a minimum Width of 25 mils. or of an inch.

I claim as my invention:

1. A laminated magnetizable core for a dynamo-electric machine comprising a plurality of stacked punchings having aligned perforations spaced somewhat from the winding-carrying periphery of the punchings, and having teeth between said perforations, characterized by the magnetizable bridges between the teeth at said periphery being slit from said perforations to said periphery, so as to provide separate teeth having peripheral portions overhanging said perforations, the aggregate peripheral width of all of the teeth being equal to the circumference of the Winding-carrying periphery of the punchings.

2. A laminated magnetizable core for a dynamo-electric machine comprising a plurality of stacked punchings having aligned perforations spaced somewhat from the winding-carrying periphery of the punchings, and having teeth between said perforations, characterized by the magnetizable bridges between the teeth at said 5 periphery being slit from said perforations to said periphery, so as to provide separate teeth having peripheral portions overhanging saidperforations, and further characterized by said teeth being bent out of the planes of the punchings.

3. The method of making punchings for the laminated magnetizable cores of dynamo-electric machines which consists in punching perfo rations spaced somewhat from the winding-carrying peripheries of the punchings and slitting the material between said periphery and the several perforations.

4. The method of making punchings for the laminated magnetizable cores of dynamo-electric machines which consists in punching perforations spaced somewhat from the winding-carrying peripheries of the punchings, slitting the material between said periphery and the several perforations, and skewing the resulting teeth out of the planes of the punchings.

ARTHUR B. REYNDERS. 

